The elevation of growth hormone (GH) levels in animals, e.g., mammals including humans, upon administration of GH-releasing compounds can lead to enhanced body weight and to enhanced milk production if sufficiently elevated GH levels occur upon administration. Further, it is known that the elevation of growth hormone levels in mammals and humans can be accomplished by application of known growth hormone releasing agents, such as the naturally occurring growth hormone releasing hormones.
The elevation of growth hormone levels in mammals can also be accomplished by application of growth hormone releasing peptides, some of which have been previously described, for example, in U.S. Pat. No. 4,223,019, U.S. Pat. No. 4,223,020, U.S. Pat. No. 4,223,021, U.S. Pat. No. 4,224,316, U.S. Pat. No. 4,226,857, U.S. Pat. No. 4,228,155, U.S. Pat. No. 4,228,156, U.S. Pat. No. 4,228,157, U.S. Pat. No. 4,228,158, U.S. Pat. No. 4,410,512, U.S. Pat. No. 4,410,513.
Antibodies to the endogenous growth hormone release inhibitor, somatostatin (SRIF) have also been used to cause elevated GH levels. In this latter example, growth hormone levels are elevated by removing the endogenous GH-release inhibitor (SRIF) before it reaches the pituitary, where it inhibits the release of GH.
Each of these methods for promoting the elevation of growth hormone levels involve materials which are expensive to synthesize and/or isolate in sufficient purity for administration to a target animal. Short chain, low molecular weight, relatively simple polypeptides which are relatively inexpensive to prepare and have the ability to promote the release of growth hormone would be desirable because they should be readily and inexpensively prepared, easily modified chemically and/or physically, as well as easily purified and formulated; and they should have excellent transport properties.
Although some short chain polypeptides which can promote the release and elevation of growth hormone levels in the blood are known, it is important to be able to tailor polypeptides for a variety of reasons, such as delivery, bioabsorbance, increased retention time, etc. However, amino acid changes at certain positions can have dramatic effects on the ability of short chain peptide to promote the release of a growth hormone.
It would be desirable to have different short chain polypeptides which can promote the release and elevation of growth hormone levels in the blood of animals, particularly in humans. It would also be useful to be able to use such polypeptides to promote the release and/or elevation of growth hormone levels in the blood of animals and humans.
It would also be desirable to provide methods for promoting the release and/or elevation of growth hormone levels in the blood of animals using such short chain polypeptides.